To sum it up ive been on a few sites with no help so far in my issue. What it does is, when i start it, it starts immediately with no issue. Starts to idle down like normal, and then begins a slightly rough idle. If i snap the throttle it stumbles and after about a second it recovers and revs up. It does this hot or cold. Also its now starting to either die or tries when i just put it in gear. Also it is running rich and plugs are blackened. i do have a scanner and everything looks ok. So far ive changed every sensor, ignition module and coils, plugs, wires. cleaned the grounds. Fuel pressure is within spec. Changed fpr, coolant sensor, head, alternator, battery. also ive noticed if i hold the rpms up and then snap it, it seems ok. Also while holding rpm, the rpm will rise and fall slightly with the o2 fliping from rich to lean. I also have currently no exhaust on it ruling that out as a plug. also egr is fine.

 

We just bought our 1990 c1500 because i couldn't pass it up. But she was running rough. I thought because she sat for two years of course its going to be a little rough. But I am still new at this and need some help too. Mine is doing the same thing